JP2019025748A - Invert off-set printing method - Google Patents

Abstract

To provide an invert off-set printing method for effectively conducting repeating printing while largely suppressing printing defect.SOLUTION: Multiwavelength reflection spectrum of an ink film obtained in an ink film formation process, which is a first process for an invert off-set printing method, to specify coating defect locations, and a coating defect printed matter is eliminated. In an ink film concentration process as a second process, multiwavelength reflection spectrum of the ink film on an elastic substrate having releasability is measured and concentration time is determined. By measuring the multiwavelength reflection spectrum of the elastic substrate is measured and presence/absence of the transfer defect, and drying time of the elastic substrate is determined. Thereby quality is improved by suppression of the printing defect, and the printed matter high in resolution is continuously manufactured.SELECTED DRAWING: Figure 4

Description

The present invention relates to a pattern forming method by reversal offset printing using an elastic substrate.

In recent years, the development of printed electronics has been remarkable, and thin and light information terminals formed by printing techniques such as displays and wearable devices formed on films have been proposed.

At present, the mainstream of transistors used in the information terminal is silicon-based, but as a manufacturing method thereof, silicon is formed by a dry method such as sputtering or CVD, and then the transistor is patterned using a photolithography technique. The method is common.

On the other hand, printed electronics for producing the transistor by a printing technique has attracted attention because it can be easily patterned on a flexible substrate typified by a plastic film at a lower cost. By using the printing technique, there are advantages such that the apparatus and manufacturing costs are lower than those of photolithography, and that a vacuum and a high-temperature process are not required, so that a reduction in energy load is achieved.

However, the printing method is generally poor in resolution as compared with the photolithography method, and fine patterning is a problem. Since the accuracy of patterning directly affects the performance of the transistor, development of a printing technique with high resolution is required.

On the other hand, there is a reverse offset printing method as an effective printing method for forming a fine pattern (Patent Document 1).

  The reverse offset printing method will be described below with reference to FIG.

(Ink film forming process)
First, the ink 2 is applied to the elastic substrate 1 having a releasable surface to obtain the elastic substrate 1a. Here, the releasability means that the ink film formed on the elastic base material is brought into contact with the printing base material 5 and transferred to the printing base material without leaving the ink film on the elastic base material. This is a known basic characteristic generally required for elastic substrates for printing.

(Ink film concentration process)
Thereafter, at least a part of the liquid components constituting the ink is evaporated or absorbed by the elastic base material to form an ink film 2a concentrated on the surface of the elastic base material to form an elastic base material 1b (FIG. 1 ( a) to (c)).

(Removal process)
Next, the elastic base material 1b is brought into intimate contact with the removal relief plate 3, the ink film is brought into contact with the removal relief plate 3 to remove unnecessary portions of the ink film, and the ink film having a printed pattern formed on the elastic base material surface. The elastic base material 1c containing 2b is obtained (FIG.1 (d)).

(Transfer process)
Next, the elastic base material 1c is brought into close contact with the printing base material 5 and separated to transfer the ink film 2b to the printing base material 5, thereby obtaining a printed matter 1d having a pattern formed on the printing base material ( FIG. 1 (e)-(f)).

(Drying process)
The elastic substrate 1 to which the transferred ink film is not attached is dried to remove the surface of the elastic substrate or a part of the liquid component absorbed by the elastic substrate.

  The elastic base material is not particularly limited as long as it has releasability that can be generally used for offset printing, and a publicly known elastic base material generally called a blanket can be used, specifically in a sheet form. Examples thereof include processed urethane rubber and polydimethylsiloxane (silicone rubber).

Here, if foreign matter adheres to the elastic base material or air bubbles are mixed in the ink in the ink film forming step, a homogeneous ink film is not formed, and a pinhole or streak-like print defect occurs. There is a case.

In addition, if the concentration is insufficient in the ink film concentration step, or concentrating too much, in the subsequent removal step, a defective print pattern formation occurs due to contact between the ink film on the elastic substrate and the removed relief plate, In some cases, sufficient resolution cannot be obtained.

Due to the printing defects derived from the ink film forming step and the ink film concentration step, there may be a problem in that a serious quality defect is caused in the intended printed matter. In particular, when a fine pattern of a transistor is formed by the above-described reverse offset printing method, the transistor performance may be deteriorated, such as a defect, disconnection, or coupling (short-circuit) in the electrode thin wire of the transistor.

In addition, when repeating printing continuously, if drying is insufficient in the drying step, the liquid component derived from ink accumulates in the elastic base material by repeating printing, and as a result, in the ink film concentration step, Since the absorption rate of the liquid component is reduced and the ink film is not sufficiently concentrated, the removal process and the transfer process are performed, so that the resolution of the printed matter may be reduced. In addition, it takes a long time to concentrate, and there is a risk that productivity will be significantly reduced.

As means for solving the above problem, a technique for detecting the presence or absence of unevenness of ink on an elastic substrate to be transferred is disclosed (Patent Document 2). Specifically, an image of an elastic substrate on which an ink film is formed is captured by a line camera, and if there is coating unevenness, the printing machine is stopped.

However, the method disclosed in the above publication can only obtain information on the captured image of the ink film. For example, it cannot obtain defect information such as the progress of local concentration, determination of blurring, and unevenness in the thickness of the ink film. I cannot get image quality.

In addition, a printing apparatus including an inspection apparatus is disclosed that transfers a pattern to be printed on an inspection roll and inspects the obtained transfer pattern before producing a printed material (Patent Document 3).

However, in the inspection method, it is necessary to install an inspection roll and an inspection device in the printing apparatus, and there is a problem in increasing the size and cost of the printing apparatus.

Further, an illuminating means for irradiating the surface of the elastic base material, an imaging means for photographing the elastic base material illuminated by the illuminating means, and an image photographed by the imaging means as image data of the elastic base material Storage means for storing and binarizing the captured image; image collating means for comparing and collating the image data stored in the storage means and image data of the next elastic base material captured by the imaging means; A determination unit that determines whether the image data collated by the image collating unit and the next image data match; and a print stop and mismatch information when the determination unit determines that they do not match A control means for informing the above and an inspection method mainly comprising the notice means are disclosed (Patent Document 4).

However, the above-described inspection method cannot measure the concentration state of the ink film on the elastic base material, which is continuously concentrated, and therefore the optimal transfer timing cannot be determined, so that there is a defect such as distortion or twist in the transfer pattern. As a result, the performance of the target transistor may be degraded.

JP 2000-289320 A JP 2007-230109 A JP 2014-159089 A Japanese Patent Laid-Open No. 2006-176861

  The problem to be solved by the present invention has been made in view of the above problems. Specifically, in the ink film forming step, the defective part of the ink film on the elastic substrate is specified and has a defect. It is characterized by eliminating printed matter, and further providing a printed matter with excellent resolution by determining the concentration time in the ink film concentration step and determining the drying time in the drying step. Defects, disconnections, and bonding of electrode thin lines printed by the method of the present invention can be greatly suppressed. That is, the present invention provides a printing method capable of greatly suppressing deterioration in transistor performance and malfunction in the formation of fine electronic circuit patterns such as transistors.

As means for solving the above problems, at least an ink film forming step of obtaining an ink film by applying ink on an elastic substrate having ink releasability; and
An ink film concentration step for concentrating the ink film;
A removing step of contacting the ink film on the elastic substrate with a removal relief plate to remove unnecessary portions from the ink film to obtain an ink film patterned on the elastic substrate;
A transfer step of contacting and transferring the patterned ink film on the elastic substrate to a printing substrate to obtain a printed material; and
A drying step of drying the elastic substrate;
In a printing method including
It is a printing method characterized by measuring a multi-wavelength reflection spectrum of an ink film obtained in the ink film forming step, specifying a coating defect portion, and eliminating a coating defect printed matter.

In the ink film concentration step described above, the concentration time of the ink film concentration step is determined by measuring a multiwavelength reflection spectrum of the ink film on the elastic base material having the ink releasability. It is a printing method.

In the transfer step described above, the printing method is characterized in that the multi-wavelength reflection spectrum of the elastic base material having ink releasability is measured to determine the presence or absence of a transfer defect.

  In the drying step described above, the printing method is characterized in that the multi-wavelength reflection spectrum of the elastic base material having ink releasability is measured to determine the drying time of the elastic base material.

The printing method according to claim 1, wherein the multi-wavelength reflection spectrum detecting means is a hyperspectral camera.

Moreover, it is a printing method of any one of Claims 1-5 whose range of the said reflection spectrum is 300 nm to 2500 nm.

The printing method according to any one of claims 1 to 5, wherein the range of the reflection spectrum is from 400 nm to 1000 nm.

According to the present invention, it is possible to reduce printing defects in reversal offset printing, and a fine pattern of a transistor having excellent resolution in which defects and disconnection are greatly suppressed is formed in an electrode thin line, resulting in deterioration in transistor performance and malfunction. Can be suppressed.

In addition, since the occurrence of a defect can be detected promptly in the ink film forming step, defective products can be excluded without performing the subsequent steps. In addition, since it is not necessary to perform plate cleaning as a post process, it is possible to contribute to reduction of waste liquid derived from plate cleaning.

According to the present invention, the surface of the elastic base material or the liquid component of the ink absorbed by the elastic base material can be detected, so that the drying time can be determined in the drying process, and the elastic base material by repeated printing can be determined. Accumulation of liquid components derived from ink can be suppressed. By suppressing the accumulation of liquid components on the elastic substrate, a constant concentration can be maintained even in the ink film concentration step, which can contribute to quality improvement and resolution improvement by suppressing printing defects.

  Concerning the resolution of printed matter, in the ink film concentration process, it is possible to detect the concentration of the ink film for each printing and determine the concentration time for a certain concentration, so that the resolution of the printed matter for each printing can be kept constant. , Transistor performance degradation can be suppressed.

It is sectional drawing for demonstrating a reverse offset printing process. It is a schematic diagram which shows the apparatus structure for implementing the reverse offset printing of this invention. It is a top view which shows an example of the removal relief plate used by the reverse offset printing of this invention. It is an example of the multi-wavelength reflection spectrum measurement result of the ink film of the ink film concentration process in Example 1 (an example in which the concentration is excessively advanced and printing is defective). It is an example of the multi-wavelength reflection spectrum change with time of the ink film in the ink film concentration step in Example 1 (an example in which the degree of concentration is appropriate and printing is good). It is an example of the multi-wavelength reflection spectrum change with time of the ink film in the ink film concentration step in Example 1 (an example in which the printing is poor due to insufficient concentration). 6 is an example of a change over time of a multi-wavelength reflection spectrum of an elastic base material in a drying process of Example 2. FIG. 6 is an example of a rate of change of a multi-wavelength reflection spectrum of an elastic base material in a drying process of Example 2. FIG.

Hereinafter, although an example of an embodiment of the present invention is explained in detail using a drawing, the present invention is not limited to these.

FIG. 1 is a diagram showing the reverse offset printing method. FIG. 2 shows an example of an apparatus configuration for carrying out the reverse offset printing method of the present invention.

  After the ink is applied to the elastic substrate 1 having a releasable surface to form the ink film 2 (ink film forming step), at least a part of the liquid constituting the ink is absorbed by the elastic substrate 1 After forming the concentrated ink film 2a (ink film concentration step), the elastic base material 1b including the ink film is brought into close contact with the removal relief plate 3, and unnecessary portions of the pattern are removed (removal step). The elastic substrate 1c is brought into close contact with the printing substrate 5, and the ink film 2b is transferred to the printing substrate 5, thereby obtaining a printed material 1d having a target pattern (transfer process). Thereafter, the elastic substrate 1 is dried (drying step).

In the ink film forming step, the ink film forming method is not particularly limited as long as it is a method capable of forming an ink film having a uniform thickness on the elastic substrate, but the slit die coating method, the bar coating method, the spin coating method, and the like. Known and publicly known ink film forming methods such as a coating method, a doctor blade method, a dispensing method, and an ink jet method can be used.

The ink is not particularly limited as long as it can be printed by the reverse offset printing method, and examples thereof include a solution in which an organic substance and a resin are dissolved, and a dispersion liquid containing a constitutional component such as metal fine particles and inorganic oxide fine particles. By forming an ink film, an insulator film, a semiconductor film, or a conductor film can be formed.

The liquid constituting the ink is not particularly limited, and an organic solvent such as water, alcohols, ketones, esters, or a mixed solution thereof can be used. In addition, the ink may contain a publicly known dispersant or additive.

  The elastic substrate generally has releasability that can be used for offset printing, that is, has a function of transferring an ink film by bringing an ink applied on the elastic substrate into contact with a plate or a printing substrate. There is no particular limitation, and a publicly known elastic base material generally called a blanket can be used.

  Such an elastic substrate has a function of absorbing liquid. For example, when ink is applied onto the elastic substrate, the ink film can be concentrated by absorbing the liquid component of the ink.

Specific examples of the elastic substrate include urethane rubber and polydimethylsiloxane (silicone rubber) processed into a sheet shape. These elastic base materials may have a laminated structure by adhering to a film layer made of a PET (polyethylene terephthalate) film, a cushion layer made of urethane sponge or the like.

In the ink film concentration step, the ink can be concentrated by evaporating a part of the liquid component of the ink or by allowing the elastic base material to absorb it. Here, due to the progress of concentration, the fluidity of the ink film is lowered and a semi-solid state is obtained. Here, when the ink film is brought into contact with the relief relief plate and the unnecessary part of the ink is removed (removal process) in a state where the ink film is not sufficiently concentrated and the fluidity of the ink film is high, the edge part near the removed part of the ink film Disturbance may occur and the resolution of the printed matter may be reduced.

Alternatively, if the ink film becomes solid due to excessive concentration, even if the ink film is brought into contact with the relief relief plate in the removal process, only unnecessary portions of the ink film cannot be removed, resulting in reduced resolution of the printed matter. There is also a case.

That is, in order to obtain printed matter with high resolution by the reverse offset printing method, it is necessary to adjust the concentration so that the ink film has an appropriate fluidity in the ink film concentration step, and the method of the present invention is used. By controlling the concentration, fine patterning applicable to the formation of electronic circuits such as transistors can be made possible.

The method of the present invention is a printing method characterized by measuring a multi-wavelength reflection spectrum of an ink film obtained in the ink film forming step, identifying a defective portion of the ink film, and eliminating printed matter containing the defect. .

The method of the present invention is a printing method characterized in that, in the ink film concentration step, the multi-wavelength reflection spectrum of the ink film on the elastic substrate is measured to determine the concentration time of the ink film concentration step. is there.

Here, the concentration rate of the ink film on the elastic substrate is influenced by the outside air temperature, humidity, air flow, or the elastic substrate surface, and the remaining amount of the liquid component derived from the ink inside the elastic substrate, and is not necessarily constant at every printing. Therefore, by determining the concentration time by the multi-wavelength spectrum measurement of the present invention in the ink film concentration step, it is possible to reduce printing defects, and for example, defects and disconnections in electrode thin wires are greatly suppressed. In addition, a fine pattern of the transistor is formed, and deterioration of the transistor performance can be suppressed.

The method of the present invention is a printing method characterized in that, in the transfer step, the presence or absence of a transfer defect is determined by measuring a multi-wavelength reflection spectrum of the elastic substrate.

  The method of the present invention is a printing method characterized in that, in the drying step, the multi-wavelength reflection spectrum of the elastic substrate is measured to determine the drying time of the elastic substrate.

  Here, in the drying step, the multi-wavelength reflection spectrum of the elastic substrate substantially includes the multi-wavelength reflection spectrum of the liquid component derived from the ink absorbed on the elastic substrate or the elastic substrate. If the liquid component contains an alcohol such as ethanol or butanol, the absorption of the hydroxyl group derived from the alcohol can be quantitatively measured at around 1700 nm.

There is no particular limitation on the method for drying the elastic substrate in the drying step, and a publicly known drying method can be used. Examples thereof include air drying, hot air air drying, and drying using a far infrared heater.

  By measuring the amount of ink-derived liquid component measured in the drying step, the degree of drying of the elastic substrate can be inspected, and the necessary drying time for preventing the liquid component from accumulating on the elastic substrate is determined. can do. As a result, it is possible to reduce printing defects. For example, a fine pattern of a transistor in which defects and disconnections are greatly suppressed is formed in the electrode thin line, and deterioration in the performance of the transistor can be suppressed.

The method for measuring the multi-wavelength reflection spectrum is not particularly limited. If the spectrum range to be measured is 300 nm to 2500 nm, or the range of the reflection spectrum is 400 nm to 1000 nm, there is no problem. Can be used as

The measurement of the multi-wavelength reflection spectrum of the present invention is not particularly limited as long as the spectrum range is 300 nm to 2500 nm, or the reflection spectrum range is 400 nm to 1000 nm and the reflection spectrum of at least two wavelengths is measured. For example, a reflection spectrum of two wavelengths of a wavelength of 450 nm and a wavelength of 600 nm may be measured, or may be continuously measured at intervals of 5 nm in a wavelength range of 500 nm to 2000 nm.

The measurement of the multi-wavelength reflection spectrum of the present invention can simultaneously measure multiple wavelength components of the reflection spectrum of the ink film and the elastic base material. In addition, since the ink film concentration and the dryness of the elastic substrate can be more accurately inspected, printing defects can be greatly reduced. For example, fine transistor patterns can be formed in which electrode defects are greatly suppressed. Thus, it is possible to suppress deterioration in the performance of the transistor.

  In addition, the multi-wavelength reflection spectrum measurement of the present invention measures the reflection spectrum of the ink film on the elastic base material having releasability or the surface of the elastic base material. Is preferred. A hyperspectral camera can be cited as a multi-wavelength reflection spectrum measuring apparatus suitable for such purposes.

Unlike a general CCD camera, a hyperspectral camera can subdivide a wide wavelength range from visible light to infrared light with a wavelength of 300 nm to 18000 nm, and acquire the light intensity (wavelength spectrum) in each wavelength range. In addition, it is possible to detect color unevenness that is difficult to identify with the naked eye, and detection of foreign matter contamination and changes with time.

In addition, a general CCD camera spectrally separates the visible light region into red, green, and blue using a color filter, etc., and obtains each image, while a hyperspectral camera spectrally separates using a diffraction grating or the like. In addition, by acquiring individual light intensities in a very narrow wavelength range, fine color information that is difficult to identify with the naked eye is discriminated, and not only in the visible light region but also in the infrared region (wavelength 700 nm to 2500 nm). Since the region can also be imaged, the physical properties and concentration of the object can be known by analyzing the spectrum.

  Therefore, in the second step of concentrating the ink film, the hyperspectral camera measures the multi-wavelength reflection spectrum of the ink film on the elastic substrate whose concentration changes rapidly, and determines the concentration time of the second step. Suitable for that.

Further, in the fourth step described above, the hyperspectral camera measures the multi-wavelength reflection spectrum of the elastic base material having the ink releasability and detects the presence or absence of a remaining ink film, thereby determining the presence or absence of a transfer defect. Suitable for judging.

Further, in the fifth step described above, the hyperspectral camera measures the multi-wavelength reflection spectrum of the elastic substrate having the ink releasability, and the presence or absence of a liquid component penetrating into the elastic substrate surface or inside, Or it is suitable for determining the drying time of the said elastic base material by measuring the quantity.

  For the printing method of the present invention, a publicly known hyperspectrum can be used, and examples include Eva Japan Co., Ltd. NH-7, SIS series, RESONON PIKA series, Headwall Photonics HyperSpec series. .

Examples The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

(Preparation for printing (ink))
As the reverse offset printing ink, a silver nanoparticle-dispersed conductive ink (15% as a solid content of silver and an average particle diameter of 20 μm) was used. The conductive ink can be printed by the method of the present invention, and then heated in an oven at 180 ° C. for 30 minutes to obtain a printed matter having conductivity.

(Preparation for printing (elastic substrate))
As the elastic substrate, a 50 mm × 50 mm square material in which a 200 μm thick silicone rubber was laminated and adhered to a 120 μm thick polyester film was used.

(Print preparation (version))
As a printing plate, a 65 mm × 65 mm square soda glass plate obtained by processing a printing pattern by a wet etching method having a thickness of 3.0 mm was used. The print pattern includes a linear pattern having a width of 100 μm and a length of 20 mm parallel to and perpendicular to the print direction (removal and transfer direction) (FIG. 3). The linear patterns were arranged at intervals of 500 μm, and 40 parallel and vertical lines were produced. In addition to the linear pattern, an observation lattice pattern (45 ° inclination, width 100 μm) and a cylindrical pattern (diameter 200 μm, staggered arrangement) were prepared.

(Preparation for printing (printing substrate))
A non-alkali glass plate having a size of 60 mm × 60 squares and a thickness of 0.7 mm was used as a printing substrate.

(Print preparation (printing device))
PE-TESTER P-100 manufactured by MHI Solution Technologies Co., Ltd. was used as a printing apparatus.

(Ink film forming process)
An ink film was formed on the elastic substrate by applying the conductive ink to the elastic substrate using a glass slit die coater.

(Concentration process)
After 30 seconds from the formation of the ink film, the entire ink film was imaged in the wavelength range of 400 nm to 1000 nm using a hyperspectral camera NH-8 manufactured by Eva Japan. Similarly, an ink film was imaged every 30 seconds. During this time, the concentration of the ink film progressed, and the ink film gradually became silvery.

(Removal process)
Subsequently, the elastic base material on which the ink film was formed was brought into close contact with the plate, and unnecessary portions of the ink film were removed by contacting with the removal relief plate to form a print pattern on the surface of the elastic base material.

(Transfer process)
Next, the printed material was obtained on the printing substrate by transferring the printing pattern to the printing substrate by bringing the elastic substrate on which the printing pattern was formed into close contact with the printing substrate and releasing it.

Similarly, printing was repeated several times, and the multi-wavelength reflection spectrum measurement, removal, and transfer of the ink film in the concentration step were performed to obtain a printed matter. At this time, the concentration time is not limited to the above 90 seconds, and printing is performed with different concentration times by setting every 30 seconds in the range of 60 seconds to 150 seconds.

  The ink film is coated on the elastic base material and then concentrated by evaporation and absorption of liquid components into the elastic base material, and gradually becomes silvery glossy. In contrast, the concentration in the central part was insufficient. As an example of the printing, after the ink film was formed by coating, it was confirmed that the entire ink film was silvery after 90 seconds had elapsed, the ink film was brought into contact with the soda glass plate, and unnecessary portions of the ink were removed. Thereafter, an ink film patterned on the elastic substrate was transferred to the printing substrate to obtain a printed matter. When the obtained printed matter was observed with a laser microscope VK-8700 manufactured by Keyence Corporation, no printing defect was observed, and the printed pattern shape was good.

(Multi-wavelength reflection spectrum analysis of ink film in concentration process)
Subsequently, the multi-wavelength reflection spectrum of the ink film imaged in the concentration step was analyzed, and the change with time of the multi-wavelength reflection spectrum was compared (FIGS. 4 to 6). As a result, it was found that the ink film made of the silver ink has a high reflection spectral intensity around 780 nm in an unconcentrated state immediately after coating, and the spectral intensity around 620 nm increases with the progress of concentration. When the reflection spectrum ratio (= 620 nm reflection spectrum / 780 nm reflection spectrum) of the concentration process in the repeated printing is calculated, if the spectrum ratio is less than 0.95, low resolution due to poor ink film concentration is confirmed. It was found that when the spectral ratio is 1.04 or more, the ink film is excessively concentrated, resulting in a film that is nearly solid, resulting in poor printing. Therefore, it was found that good printed matter can be obtained when the spectral ratio is 0.95 or more and less than 1.04 regardless of the concentration time.

However, with respect to the reflection spectral ratio of the ink film, the wavelength to be selected differs depending on the ink used, and the optimum range of the spectral ratio is also different. Therefore, after obtaining the relationship between the concentration of the ink film and the spectrum for each ink to be used and determining the range of the optimum spectral ratio, continuous printing is performed. Therefore, the multi-wavelength reflection spectrum to be analyzed and the spectrum ratio are not limited to the present embodiment.

(Continuous printing)
Continuous printing was performed by repeating a series of reverse offset printing steps from the ink film formation to the transfer step 20 times. After the ink film was formed by coating, imaging with the hyperspectral camera was performed in the ink film concentration step of each printing every 30 seconds, and the reflection spectrum of the entire ink film was measured. After confirming that the reflection spectrum ratio at the central portion of the ink film was 0.95 or more and less than 1.04, the removal step and the transfer step were performed. At this time, since the liquid component absorption derived from the ink was accumulated in the elastic substrate, the time required for the concentration was increased every time printing was repeated, but the printing could be repeated 20 times continuously without any problem.

(Print evaluation)
When the obtained printed matter was observed with a laser microscope after 20 continuous printings, almost no printing defects were observed, and the resolution of the printed pattern was high and good. In addition, after the printed matter was heated and heated in an oven at 180 ° C. for 30 minutes, the resistance value of the linear pattern described above (total of 80) was measured using XYC HiTESTER manufactured by Hioki Electric Co., Ltd. Inspection of disconnection and short circuit revealed no defects (Table 1).

(Coating defects)
Further, in the continuous printing, by measuring the multi-wavelength reflection spectrum of the ink film of the present invention, it is possible to detect a coating failure from the captured image. That is, in the ink film formation process, if it is confirmed from the captured image or the reflection spectrum data that the ink film is crushed or pinholes and a uniform ink film is not formed, printing is immediately stopped, Continuous printing can be continued by removing the defective ink film from the elastic substrate.

For example, in Example 1, since an ink film formation failure due to the occurrence of pinholes occurred at the 13th printing, printing was interrupted and the defective ink film was removed. If the formation of a defective ink film is overlooked, a defective printed matter is generated and a load of plate cleaning work is added, which is not preferable because productivity is greatly reduced. In general, the ink film formed in the ink film forming process of the reverse offset printing is a thin film and is transparent depending on the type of ink, so that visual discrimination is difficult. By the multi-wavelength reflection spectrum measurement of the present invention and the visualization based on the spectrum data of the captured image, it becomes significantly easier to discriminate defects as compared with visual observation. Therefore, by using the method of the present invention, it is possible to perform the removal, transfer, and plate cleaning steps while reducing the productivity and the ink film being defective, and the resulting increase in the amount of waste liquid derived from the plate cleaning step can be suppressed.

(Transfer defects)
In the continuous printing transfer step, the presence or absence of transfer defects can be determined by measuring the multiwavelength reflection spectrum of the ink film of the present invention. That is, in the removal step or the transfer step, if the ink film does not move from the elastic base material to the plate or the printing base material and remains on the elastic base material, by measuring the multi-wavelength reflection spectrum of the present invention, Since the spectrum derived from the ink film is detected, the presence or absence of a defect can be determined.

For example, in the transfer process of the eighth printing in Example 1, since the residual ink film is detected on the elastic base material from the image captured by the hyperspectral camera, that is, the transfer failure is confirmed, the printing is interrupted and the elastic base material is defective. The ink film was removed. By using the method of the present invention, it is possible to promptly detect printing defects in continuous printing, and thus it is possible to greatly suppress a decrease in productivity.

(Comparative Example 1)
Except for fixing the concentration time in the ink film concentration step to 90 seconds, after performing the print preparation in the same manner as in Example 1, reverse offset printing was continuously performed (ink film imaging, multi-wavelength reflection spectrum). Measurement is not performed). Transfer defects occurred continuously in the 10th and 11th printing. The residual ink film on the elastic substrate was visually confirmed. Further, in the twelfth and thirteenth printing removal steps, removal defects caused by the unconcentrated ink film coming into contact with the plate were confirmed. Furthermore, in the 14th and 15th ink film forming steps, a pinhole-like ink film formation defect thought to be caused by some ink film removal defects occurred, and thus continuous printing was stopped. Moreover, in the electrical property evaluation after printing, it was confirmed that many disconnections and shorts occurred in the printed material after the seventh printing, and it was confirmed that no print quality was obtained (Table 2). From the microscopic observation of the printed matter, it was confirmed that the overall resolution was low after the seventh printing.

(Preparation for printing (ink))
The same procedure as in Example 1 was used except that a UV curable styrene acrylic resin propylene glycol monomethyl ether acetate (hereinafter, PGMEA) solution (20% as solid content, almost colorless) was used as the insulating ink for reverse offset printing. Prepared for printing. After printing by the method of the present invention, the insulating ink film patterned on the printing substrate is cured with an integrated light quantity of 2000 mJ / cm 2 using a UV irradiation device equipped with a high-pressure mercury lamp, thereby providing insulation. It can be set as a transparent printed matter.

(Preparation for printing (elastic substrate, plate, printing substrate)
In the same manner as in Example 1, materials and devices other than ink were prepared for printing.

(Ink film forming process)
In the same manner as in Example 1, an ink film was formed on the elastic substrate.

(Concentration process)
After the ink film was formed, the entire ink film was imaged in the near-infrared region with a wavelength range of 1000 nm to 1600 nm using a hyperspectral camera SIS-1 manufactured by Eva Japan. Whether or not a good ink film is formed in the ink film forming step cannot be determined by visual observation because the ink film is a transparent thin film, but can be determined from a captured image in the near infrared region of the present invention. In the insulator ink, the ink film formation state was judged from the reflection spectra of 1320 nm and 1420 nm (FIG. 7). If it is confirmed from the captured image and the reflection spectrum that a good ink film is not formed, printing is interrupted immediately, and the subsequent steps are not performed, so that the productivity drop can be suppressed and the plate is washed. It is possible to reduce the load of using the cleaning liquid and waste liquid treatment.

After confirming that a good ink film has been formed from the imaging, the liquid component of the ink film is absorbed by the elastic base material or volatilized for 90 seconds to advance the concentration of the ink film. It was. At this time, the ink film gradually changed to a transparent film.

(Removal process)
In the same manner as in Example 1, the elastic base material on which the ink film was formed was brought into close contact with the plate, and unnecessary portions of the ink film were removed by contacting the removal relief plate to form a print pattern on the surface of the elastic base material. did.

(Transfer process)
In the same manner as in Example 1, the printed pattern is formed on the printing substrate by transferring the printing pattern to the printing substrate by bringing the elastic substrate on which the printing pattern is formed into close contact with the printing substrate and releasing it. Printed material was obtained.

(Drying process)
The transferred elastic substrate was imaged every 30 seconds in the wavelength range of 1000 nm to 1600 nm using the hyperspectral camera SIS-1. From the multi-wavelength reflection spectrum acquired based on the captured image, an ink-derived liquid component seen as PGMEA permeating into the elastic base material or inside the elastic base material was confirmed. Further, as a result of imaging every 30 seconds, it was confirmed that the ink-derived component was reduced as the drying progressed. The ink-derived component is a volatile liquid such as PGMEA, and is volatilized by blowing air in the drying process and is considered to be gradually removed from the elastic substrate. By inspecting the dryness of the elastic substrate by the method of the present invention, the shortest time required for drying can be determined, so that the printing time can be shortened and contributes to minimizing the air flow required for drying. it can.

(Multi-wavelength reflection spectrum analysis of ink film in drying process)
The multi-wavelength reflection spectrum (FIG. 7) of the ink film imaged in the drying process was analyzed, and the change with time of the multi-wavelength reflection spectrum as the drying progressed was tracked (FIG. 8). It was confirmed that the rate of change of the multi-wavelength reflection spectrum decreases with the progress of drying. It was confirmed that repeated printing was possible by drying the elastic substrate until the rate of change was less than 1.01 in the measurement wavelength range of 1000 nm to 1600 nm. Since the rate of change at which repeated printing is possible varies depending on the ink used, the multi-wavelength reflection spectrum of the elastic substrate is measured for each ink used, and the rate of change is derived from the change over time. After obtaining the relationship and determining the required drying time, continuous printing is performed. Therefore, the multi-wavelength reflection spectrum to be analyzed and the rate of change are not limited to the present embodiment.

(Continuous printing)
The multi-wavelength reflection spectrum of the elastic base material was measured in the drying step, and after the spectrum was judged to hardly change over time and the ink-derived component was hardly left, air drying was terminated, and the following By performing printing, it is possible to stably and repeatedly perform printing. If the elastic substrate is repeatedly dried with insufficient drying of the elastic substrate, liquid components derived from ink accumulate on the surface or inside of the elastic substrate, resulting in poor ink film formation and longer concentration time. This is not preferable because it hinders stable continuous printing. Also, if the drying time by blowing is excessively long, the printing process is prolonged, leading to an increase in energy usage accompanying the blowing, which is not preferable. According to the reverse offset printing method for measuring a multi-wavelength spectrum of the present invention, an appropriate drying time can be set for each printing, and as a result, a stable printing can be carried out, and a printed matter with greatly reduced printing defects. Can be obtained efficiently.

(Print evaluation)
After printing 20 times continuously, the obtained printed matter was observed with a laser microscope. As a result, almost no printing defects were found and the printing pattern was good. Further, by measuring the capacitance between the above-described linear pattern (total of 80) and the bottom surface of the printing substrate using an XYC HiTESTER manufactured by Hioki Electric Co., Ltd., the linear pattern is disconnected and adjacent. When the connection of the straight line patterns was inspected, the number of these defects was 1 or less, which was good (Table 3).

(Coating defects)
In Example 2, a streak-like coating defect was detected in the coating direction from the multi-wavelength reflection spectrum measurement in the near-infrared region of the present invention, so printing was interrupted and the defective ink film was removed. did. At this time, since the ink film was transparent, it was impossible to detect defects visually. After removing the ink film containing the coating defect, continuous printing was resumed.

(Transfer defects)
In Example 2, since the remaining of the ink film on the elastic base material due to transfer failure was detected at the fifth printing from the multi-wavelength reflection spectrum measurement in the near-infrared region of the present invention, the printing was interrupted, and the defective ink film Was removed. At this time, since the ink film was transparent, it was impossible to detect defects visually. After removing the ink film remaining on the elastic substrate, continuous printing was resumed.

By detecting defects by the multiwavelength reflection spectrum measurement of the present invention, both coating defects and transfer defects can detect defects that cannot be detected visually or with a CCD camera or the like. By using the method of the present invention, it is possible to suppress a decrease in productivity and an increase in the amount of waste liquid accompanying plate washing.

(Comparative Example 2)
Except for fixing the concentration time in the ink film concentration step to 90 seconds, the preparation for printing was performed in the same manner as in Example 2, and then reverse offset printing was continuously performed (imaging film imaging, multi-wavelength reflection spectrum). Measurement is not performed). Since the ink film is transparent, defects, transfer defects, etc. cannot be judged visually, and printing was carried out for a predetermined 20 consecutive times (see FIG. 4). After that, the resolution of the printed material was evaluated by microscopic observation, and further, the disconnection of the linear pattern shown in FIG. 3 and the short circuit (connection of the linear pattern) were inspected using a high tester. As a result, a good print was not obtained. In addition, despite the fact that a good printing product could not be obtained, the washing waste liquid from the plate cleaning performed every printing was accumulated, and the productivity was lowered.

1: Elastic base material 1a: Elastic base material 1b coated with an ink film: Elastic base material 1c formed with an ink film 2a: Elastic base material 1d formed with an ink film 2b: Printed material 2: Ink film 2a: Concentration Ink film 2b: Ink film 2c patterned on elastic substrate surface: Ink film removed on removal relief plate 3: Removal relief plate 4: Removal relief plate with ink film attached 5: Printing substrate 6: Rotating drum 7: Rail 8 on which the surface plate travels: Hyperspectral camera 9: Lamp 10: Image output terminal 11: Elastic substrate drying device 12: Air

Claims (7)

At least a first step of obtaining an ink film by applying ink on an elastic substrate having ink releasability;
A second step of concentrating the ink film;
A third step of obtaining an ink film patterned on the elastic base material by contacting the ink film on the elastic base material with a removing relief plate to remove unnecessary portions from the ink film;
A fourth step in which the patterned ink film on the elastic substrate is contact-transferred to a printing substrate to obtain a printed matter;
A fifth step of drying the elastic substrate;
In a printing method including
A printing method comprising measuring a multi-wavelength reflection spectrum of an ink film obtained in the first step, identifying a coating defect portion, and eliminating a coating defect printed matter.   2. The printing process according to claim 1, wherein a multi-wavelength reflection spectrum of an ink film on the elastic base material having ink releasability is measured to determine a concentration time of the second process. Method.   The printing method according to claim 1, wherein the multi-wavelength reflection spectrum of the elastic base material having ink releasability is measured to determine the presence or absence of a transfer defect.   The printing method according to claim 5, wherein the drying time of the elastic substrate is determined by measuring a multi-wavelength reflection spectrum of the elastic substrate having ink releasability.   The printing method according to claim 1, wherein the multi-wavelength reflection spectrum detecting means is a hyperspectral camera. The printing method according to any one of claims 1 to 5, wherein a range of the reflection spectrum is 300 nm to 2500 nm.   The printing method according to claim 1, wherein a range of the reflection spectrum is 400 nm to 1000 nm.

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